Some medical devices used for therapy or surgery, e.g., a linear accelerator (LINAC) or a cobalt teletherapy unit, or for imaging, e.g., CT scanners, incorporate a large gantry rotating about a patient. Upgrading older units (e.g., a LINAC), by adding imaging equipment on the rotating gantry would allow an efficient way to perform advanced treatments such as Image-Guided Radiotherapy (IGRT). However, mounting additional devices (e.g., collimators, radiation sources or imaging equipment) on the rotating gantry is limited due to the gantry's mechanical constraints.
LINAC manufacturers (e.g., Siemens, Varian, Electa, Tomotherapy) have introduced new devices designed to incorporate such additional imaging functions on the rotating gantry. Other manufacturers (e.g., BrainLabs, Accuray) utilize additional imaging equipment that is floor or ceiling-mounted.